1. Field of the Invention
The present invention relates to a method for packaging a target material and a method for mounting a target on an apparatus. Specifically, the present invention relates to a method for packaging a sputtering target material containing a deposition material and a method for mounting a target on a deposition apparatus.
2. Description of the Related Art
A physical vapor deposition method with the use of a target enables thin films of a variety of materials to be formed. Examples of a physical vapor deposition method with the use of a target include a sputtering method and a pulsed laser deposition method. In particular, with a sputtering method, a film can be easily formed over a large-area substrate, and further, even a material whose melting point is high and whose vapor pressure is low can be deposited, for example. In addition, by introducing a reactive gas into a deposition chamber, metal oxide, metal nitride, and the like can be deposited over a substrate. Furthermore, a sputtering method has merits such as relatively less damage to a substrate and is one of important techniques in thin film formation.
In a sputtering method, a target material (a material used for sputtering) is used as a source material; therefore, the characteristics of a thin film which is formed are adversely affected by dusts or impurities attached to the target material. Accordingly, various techniques for preventing contamination of the target material have been disclosed. For example, a packaging technique for protecting the surface of a target material has been disclosed in Patent Document 1.
In addition, a technique of forming an oxide semiconductor film over a substrate such as a glass substrate, manufacturing a transistor using the oxide semiconductor film, and applying the transistor to an electronic device or an optical device has been attracting attention. For example, Patent Document 2 and Patent Document 3 disclose a technique by which a transistor is manufactured using zinc oxide or an In—Ga—Zn—O-based oxide semiconductor as a semiconductor material and such a transistor is used as a switching element or the like of an image display device.
An oxide semiconductor film can be formed at relatively low temperature by a sputtering method or the like and is suitable for a thin film transistor (also referred to as a TFT). A manufacturing process of a TFT using an oxide semiconductor film is simpler than that of a TFT using a polycrystalline silicon film. In addition, a TFT in which a channel formation region (also referred to as a channel region) is provided in an oxide semiconductor can have higher field effect mobility than a TFT using amorphous silicon.
Transistors which include oxide semiconductors can be formed not only over a glass substrate but also over a plastic substrate and thus are expected to be applied to display devices such as liquid crystal displays, electroluminescent displays (also referred to as EL displays), or electronic papers.